Shortly after WW1, and before he became the head of the FBI, J. Edgar Hoover spent some time in Hollywood, urging film makers to curtail certain kinds of film making which he felt did not serve the best interests of the country. In particular, Hoover did not like the films of Charles Spencer Chaplin which tended to show people in authority abusing their power, maltreating common people, and eventually being made to look ridiculous. It was a Chaplin trademark, one which Hoover felt fostered a disrespect for authority in the general population.
Chaplin not only ignored Hoover's entreaties, but made fun of him, and when Hoover ascended to the head of the FBI, he made Chaplin pay for his earlier insults, and was instrumental in having Charlie kicked out of the United States.
Hoover was also quite eager to use his new authority to bring Hollywood into line with what Hoover thought was their proper role in society (propaganda organ for the government) and while Senator McArthy grabbed the headlines, Hoover was busy behind the scenes recruiting various people to inform on each other and factionalizing the Hollywood community so that it could not resist him.
One interesting story from those days relates to famed animator Walt Disney who had earlier on asked for Hoover's help in locating his real birth parents, little realizing the price Hoover would make him pay later. During the McCarthy hysteria, Hoover asked Walt Disney to report on anyone that might be a communist. Walt actually did on so at just one occasion, yielding to what must have been an overwelming temptation.
Years ealier, Walt Disney had been teamed up with another animator named Walter Lantz, and together they produced a cartoon named "Oswald The Rabbit", created by Disney. But when their partnership dissolved, somehow Walter Lantz retained ownership of Oswald. On the long train ride home, Walt Disney sketched himself a small rodent with big ears and rubber hose arms and legs and named him "Mortimer Mouse". Following a slight name change by Walt Disney's wife, the new Disney star was born, and Disney became a household name. Walter Lantz went on to create his own star, "Woody Woodpecker".
When Hoover approached Disney to be an informant, Walt was hardly sympathetic. His studio had been stiffed on the payment for several training films produced for the Army during WW2. But the opportunity to "get" the man who stole Oswald from him was too great, and Walt Disney named Walter Lantz to the House Committee on Un-American Activities. That was Walt Disney's fatal mistake.